This section provides background information related to the present disclosure which is not necessarily prior art.
Cooling systems are utilized for air conditioning as well as for refrigeration of food products. Variations in performance and/or breakdown of the cooling systems can negatively affect health and comfort of humans, safety of food products and/or profitability of a business. Cooling systems have applicability in a number of different applications where a fluid is to be cooled. The fluid may be a gas, such as air, or a liquid, such as water. Example applications are heating, ventilation, air conditioning (HVAC) systems that are used for cooling spaces where people are present such as offices and data center climate control systems. A data center may refer to a room having a collection of electronic equipment, such as computer servers.
In FIG. 1, an air conditioner 50 that may be used in, for example, a computer room is shown. The air conditioner 50 includes a cooling circuit 51 and a cabinet 52. The cooling circuit 51 is disposed in the cabinet 52 and includes an evaporator 54, an air moving device 56, a compressor 58, a condenser 60, and an expansion valve 62. The evaporator 54, compressor 58, condenser 60 and expansion valve 62 are connected in a closed loop in which a cooling fluid (e.g., phase change refrigerant) circulates. The evaporator 54 may include a V-coil assembly with multiple cooling slabs to provide increased cooling capacity. The evaporator 54 receives the cooling fluid and cools air passing through openings in evaporator 54. The air moving device 56 (e.g., a fan or squirrel cage blower) draws the air from an inlet (not shown) in the cabinet 52 and through the evaporator 54. The cooled air is directed from the evaporator 54 and out a plenum 64 in the cabinet 52.
The compressor 58 circulates the cooling fluid through the condenser 60, the expansion valve 62, and the evaporator 54 and back to the compressor 58. The cooling fluid is received at an inlet of the compressor compressed and discharged at a center (or outlet) towards the condenser 60. The condenser 60 cools the cooling fluid received from the compressor 58. The expansion valve 62 may be an electronic expansion valve and expand the cooling fluid out of the condenser 60 from, for example, a liquid to a vapor.
A position of the expansion valve 62 (or opening percentage of the expansion valve) may be adjusted to control a suction superheat value of the compressor 58. The suction superheat value of the compressor is equal to a compressor suction temperature minus a compressor saturated suction temperature. A compressor suction pressure may be used to determine the compressor saturated suction temperature. The compressor suction temperature and the compressor suction pressure may be determined based on signals from corresponding sensors connected between the evaporator 54 and the compressor 58. The superheat value refers to an amount that a temperature of a cooling fluid, in a gas state, is heated above the compressor saturated suction temperature.
The superheat value can be used to modulate (or adjust) position of the expansion valve 62. Position (or opening percentage) control of the expansion valve 62 may be performed by a proportional, integral, derivative (PID) control module. The PID control module controls the superheat value to match a constant predetermined superheat setpoint. This ensures compressor reliability and improves compressor efficiency.
Components of air conditioning systems can degrade over time. The degradation can result in refrigerant leakage, fouling of a condenser coil, clogging of a filter dryer and/or an air filter, compressor wear, etc. A refrigerant leak can damage a compressor and/or be harmful to an environment. The degradation of the components can cause inefficient system operation and/or downtime if one or more of the components fail.